The invention claims priority under 35 USC xc2xa7119 to United Kingdom application No. 9709500.4, filed May 9, 1997.
The present invention relates to a mould for individual casting of soft solid articles. The invention more particularly refers to essentially a split cavity mould comprising of at least two rigid dies. Another aspect of the invention relates to a process of casting a melt in such said moulds for individually producing shaped articles of soap and/or non-soap detergent.
1. Field of the Invention
The subject invention relates to soap bars made using bar casting technology and to molds used in the casting of the bars. In particular, the invention relates to rigid complimentary dies defining a cavity and used for making shaped, solid detergent articles.
2. Description
Soap or non-soap detergent articles are traditionally produced by shear working/homogenisation of the formulation followed by extrusion and stamping. This procedure is only suitable for detergent bar formulations which are thermoplastic or which are not shear sensitive. While some transparent soap formulations can be produced by this route many other formulations which are very shear sensitive can not be so produced in bar form and special processing techniques have to be employed for their manufacture, known examples of which are given below.
Casting of a Melt into Bars:
This process is employed for producing highly transparent soaps. The technology presently employed involves many manufacturing operations such as casting of molten soap into long bars of desired cross section (Schist moulds), cooling, bar ejection, bar maturation, billeting, chamfering, billet maturation and stamping to produce individual transparent soap tablets. Although the maturation time may be reduced or completely eliminated by employing certain formulation variations, overall this process is highly labour intensive and is very expensive.
Casting in Pack:
This process involves casting a molten soap blend into a shaped transparent pack or sachet, in which it is solidified and sold as such. Although highly transparent soaps can be produced by this technology, the process is very expensive and maturation, if required, is very slow.
Individual Casting in Flexible Moulds:
Individual casting of transparent soap tablets has been disclosed in JP 61026699 (Kanebo, Ltd., 1984). This describes a method involving casting a melt into a xe2x80x9cthin moulding platexe2x80x9d which is flexible or elastic and is made of synthetic resins. This disclosure simplifies the manual operations involved in the conventional technology of making transparent soaps by eliminating the steps of billeting, chamfering, stamping and polishing. However, the process has inherent disadvantages such as unattractive and non-reproducible appearance/shape of tablets, poor surface finish and shorter mould life.
It is therefore an object of the present invention to provide a rigid two part split mould for individual casting of solid shaped detergent articles such as soap/non-soap detergent tablets which gives an unblemished and bubble free product in a form that is dictated by the shape of the mould. Furthermore the mould is designed for efficient cooling of the cast article.
Thus, the present invention provides a mould for casting shaped, solid detergent articles, comprising at least two rigid complimentary dies which upon engagement define a cavity corresponding to a desired shape of the cast article, wherein the engaged dies form a reservoir which on one side is open to receive cast melt and on another side is open to the cavity.
The reservoir opens on one side to the cavity and on the other side has a feed opening to fill the mould. Preferrably, the die is designed in a manner such that the volume ratio of the reservoir to the cavity is at least 5%. Leakage of liquid from the mould is prevented by the engagement of the two dies.
Optionally the inside surface of the said cavity is provided with mirror images of inscriptions desired on the surface of the cast article. The said dies are preferably hinged, and the external surface of the said dies is preferably provided with means to improve cooling of the mould after casting, such as fins/ribs for air cooling or jackets for circulation of a coolant liquid. The thickness and width of the rim are so designed that the cooling takes place relatively faster in the region of the rim.
According to a further aspect of the invention, a process is provided for the manufacture of solid shaped detergent articles comprising the steps of:
i. making a melt of the composition to be cast;
ii. pouring the said melt into the above described mould;
iii. cooling the mould to promote solidification;
iv. demoulding the solidified shaped article.
Preferrably, the mould is preheated before the melt is poured therein such that the internal surface of the mould is at a temperature above the solidification temperature of the melt.
The process is suitable for manufacturing shaped detergent articles such as tablets of soap and/or non-soap detergent, for example for personal washing or for washing fabric.
Most particularly the process may be used for manufacturing transparent tablets for personal wash. Depending on the formulation and the desired transparency of the product, such tablets are preferably matured after demoulding.
The process may be carried out in a continuous manner by having a plurality of moulds circulating through a melt feeding station where each mould is filled with the melt and subsequently taken through the steps of cooling to complete solidification and demoulding before being recycled again.